用提示創建一個網頁

Question

我的提示框不起作用？自從我把元素的東西放在那裏不工作。

我需要提示框，以便我可以輸入信息，然後該信息自動進入表格，然後通過在表格的行中自動讀取最大金額$。我不是100％的js編碼，所以不要笑，如果它是一個簡單的修復（這是簡單的事情，讓我）。

這是我的代碼，我不知道我做錯了

「我的表是在頭」

function money(){ 

this.currency = ""; 
this.amount = ""; 
this.exchangeRate = ""; 
this.ausDollars = ""; 

tbody = document.getElementsByTagName('tbody')[0]; 
for (var i = 0; i <= 3; i++) 
    trElement = document.createElement('tr'); 
    tbody.appendChild(trElement); 

// Read the 3 letter currency abbreviation entered 
    currency = prompt('Please enter a 3-letter currency abbreviation', +i, ""); 
    // If the input data is invalid ask the user to re-enter it 
    while (currency.length != 3) { 
    currency = prompt('Currency abbreviation was not entered', ""); 
    currency = parseFloat(currency); 
    } 

currencyTH = document.createElement('th'); 
    currencyText = document.createTextNode(currency); 
    currencyTH.appendChild(currencyText); 
    trElement.appendChild(currencyTH); 

// Read the amount and convert it to entered currency 
    amount = prompt('Please enter an amount of money in that currency', +i, ""); 
    // If the input data is invalid ask the user to re-enter it 
    while (isNaN(amount) || amount < 0) { 
    amount = prompt('An amount of money was not entered') 
    amount = parseFloat(amount); 
    } 

amountTH = document.createElement('th'); 
    amountText = document.createTextNode(amount); 
    amountTH.appendChild(amountText); 
    trElement.appendChild(amountTH); 

exchangeRateTH = document.createElement('th'); 
    exchangeRateText = document.createTextNode(exchangeRate); 
    exchangeRateTH.appendChild(exchangeRateText); 
    trElement.appendChild(exchangeRateTH); 

} 

Answer 1

的問題是，你正在使用prompt()到都提示用戶輸入和與用戶輸入有關的顯示錯誤消息。爲此，您正在尋找alert()。

首先，你設定的貨幣提示與：

currency = prompt('Please enter a 3-letter currency abbreviation', +i, ""); 

然後運行：

currency = prompt('Currency abbreviation was not entered', ""); 

這覆蓋，最初存儲在currency價值，所以你無法在下一行上運行parseFloat()：

currency = parseFloat(currency); 

要解決此問題，使用方法：

alert('Currency abbreviation was not entered'); 

請注意，這是amount同一案件。相反的：

amount = prompt('An amount of money was not entered'); 

用途：

alert('An amount of money was not entered'); 

另外請注意，您的while循環結構稍有不當無限期提示，直到正確的值被滿足。除了最初的提示，然後運行while循環，你應該在循環之外設置一個變量，然後檢查條件。而parseFloat()必須出現在while循環之外，否則你將陷入無限循環！

var currency = ''; 
 
currency = prompt("Please enter 3 characters"); 
 
while (currency.length != 3) { 
 
    alert('Currency must be three characters'); 
 
    currency = prompt("Please enter 3 characters"); 
 
} 
 
currency = parseFloat(currency); 
 

 
console.log("The stored value was: " + currency);

希望這有助於！ :)